Sample-analysis system with antisynchronously driven contactless conductivity detector

Abstract

In a differential condition, an electrophoresis system antisynchronously drives a longitudinally-separated pair of contactless drive electrodes, both of which are coupled to a detection electrode through a separation channel. In this condition, the system provides a series of peaks readout in ITP-separation mode. In a direct condition, the system antisynchronously drives a pair of drive electrodes, only one of which is coupled to the detection electrode through the channel; the other is coupled to the detection electrode but not though the channel. In this condition, the system provides a series of peaks readout in CZE mode. In either case, the antisynchronous drive enhances the detection signal by canceling at the detection electrode signal components associated with the AC drive source. Similar advantages are achieved for a capillary differential electrophoresis system and for a planar direct electrophoresis system.

What is claimed is:  
     
       1. A sample-analysis system comprising: 
       a separator for separating sample components as they move along a longitudinally extending channel, said separator including said channel;  
       a detector for detecting sample components moving along said channel, said detector including:  
       a detection electrode capacitively coupled to said channel;  
       longitudinally separated first and second drive electrodes, said first drive electrode being electrically coupled to said detection electrode through said channel;  
       drive means for driving said first and second drive electrodes antisynchronously, said drive means being electrically coupled to said drive electrodes; and  
       a signal processor for providing a readout signal representing the contents of said channel as said sample components move past said detection-electrode set.  
     
     
       2. A sample-analysis system as recited in  claim 1  wherein said second drive electrode is coupled to said detection electrode through said channel. 
     
     
       3. A sample-analysis system as recited in  claim 2  wherein said separator includes an ITP mode in which sample components are separated by isotachophoresis, said signal processor providing said readout signal as a series of peaks when said separator is in said ITP mode. 
     
     
       4. A sample-analysis system as recited in  claim 3  wherein said separator includes a CZE mode in which sample components are separated by chemical-zone electrophoresis, said signal processor including an integrator for providing said readout signal as a series of peaks when said separator is in said CZE mode. 
     
     
       5. A sample-analysis system as recited in  claim 1  wherein said detection electrode is disposed longitudinally between said first and second drive electrodes. 
     
     
       6. A sample-analysis system as recited in  claim 1  wherein said detection electrode is spaced from said first drive electrode transversely by said channel. 
     
     
       7. A sample-analysis system comprising: 
       a separator for separating sample components as they move along a longitudinally extending channel, said separator including said channel, said separator providing an ITP mode in which sample components are separated by isotachophoresis; and  
       a detector for detecting sample components moving along said channel, said detector including  
       a detection electrode capacitively coupled to said channel,  
       first and second drive electrodes, said first drive electrode being electrically coupled to said detection electrode through said channel,  
       drive means for driving said first and second drive electrodes antisynchronously, said drive means being electrically coupled to said drive electrodes,  
       a signal processor for providing a readout signal representing the contents of said channel as said sample components move past said detection-electrode set, said signal processor providing said readout signal as a series of peaks when said separator is in said ITP mode,  
       a third electrode electrically coupled to said detection electrode but not through said channel, and  
       a switch having differential and direct conditions, said switch when in said differential condition coupling said drive means to said first and second drive electrodes to drive them antisynchronously, said switch when in said direct condition coupling said drive means to said first and third drive electrodes to drive them antisynchronously.  
     
     
       8. A sample-analysis system as recited in  claim 7  wherein said separator includes a CZE mode in which sample components are separated by chemical-zone electrophoresis, whereby 
       when said separator is in said CZE mode and said switch is in said direct condition, said signal processor provides a series-of-peaks readout in which the peaks represent sample component peaks, and  
       when said separator is in said ITP mode and said switch is in said differential condition, said signal processor provides a series-of-peaks readout in which the peak represent boundaries between sample-component bands.  
     
     
       9. A sample-analysis system comprising: 
       a separator for separating sample components as they move along a longitudinally extending channel, said separator including said channel;  
       a detector for detecting sample components moving along said channel, said detector including  
       a detection electrode capacitively coupled to said channel,  
       first and second drive electrodes, said first drive electrode being electrically coupled to said detection electrode through said channel, said second drive electrode being electrically coupled to said detection electrode but not through said channel,  
       drive means for driving said first and second drive electrodes antisynchronously, said drive means being electrically coupled to said drive electrodes, and  
       a signal processor for providing a readout signal representing the contents of said channel as said sample components move past said detection-electrode set.  
     
     
       10. A sample-analysis system as recited in  claim 9  wherein said separator includes a CZE mode in which sample components are separated by chemical-zone electrophoresis, said signal processing means providing said readout signal as a series of peaks when said separator is in said CZE mode. 
     
     
       11. A sample-analysis system as recited in  claim 10  wherein said separator includes an ITP mode in which sample components are separated by isotachophoresis, said signal processing means including a differentiator for providing said readout signal as a series of peaks when said separator is in said ITP mode.